chris French wrote:
In message ,
writes
In uk.d-i-y, David Hearn wrote:
The guttering of our house is about 5.5m above the ground. I want
a ladder which will reach that height safely. I've no plans on
doing any serious work up there

[ ... ]

What is the recommended angle for ladders? If I need to reach 5.5m
vertical and the ladder is at the recommended angle - what length
(extended) ladder do I require? I've been looking at 7m+ ones -
though I'm wondering whether
6.5m will be sufficient.

I'm pretty sure the suggested ratio is 1:4; that's what a moment's
Google with the words "ladder angle safe" produces, too. The less
helpful sites say "75 degrees";

Thus, for a vertical reach of 5.5m, at the 1:4 ratio, Mr Pythagoras
says you'll want a hypotenuse of at least sqrt( 5.5^2 + 1.4^2 ) =
5.7m (minimally longer than the long side, since at these small
angles,
sin(x) is only just a little less than x).

However, the ladder specs may be a little optimistic about the full
extension: to stop it bouncing alarmingly when you reach the middle
in your tapdance up the rungs, you may want a bit more overlap than
the 2-3 rungs which full extension is quoted at. So a 6.5m ladder
would have just 0.8m of overlap if two-section; you might prefer the
greater rigidity of the 7m flavour, especially if your physique is
closer to "cuddly" than "boney" ;-)

I'd also want to allow for say 1/2 metre above the gutter as something
to hold onto etc. when working.

So the 7m+ 3 section ladder is likely to be just right, with any excess
being able to allow more overlap and less bounce.... I'm certainly not
'boney' and just on the limit for domestic ladders (without wearing shoes or
carrying tools!) so I'll listen to your advice.

Thanks

David